Place thawed tuna steaks in a bowl or a sealed plastic bag.
Combine the soy sauce, ginger, sesame oil, olive oil, lime juice, and red chili sauce and pour the mixture over the Ahi tuna steaks.
Seal or cover and place the tuna steaks in the fridge and marinate for at least 30 minutes.
Remove the tuna steaks from the fridge and take out of the marinade.
Top each tuna steak with sesame seeds.
Heat oil in a large skillet set over high heat. Add one tuna steak to the pan and sear for 30 seconds to 2 minutes on each side.
Repeat for each tuna steak.
Allow the tuna steaks to rest for 2 minutes and then thinly slice.